The present invention relates to a coordinate input apparatus for inputting three-dimensional coordinates or two-dimensional coordinates and a control method thereof, and a computer readable memory.
A conventional system handling three-dimensional coordinates, e.g., three-dimensional CAD, three-dimensional layout tools, three-dimensional motion games, three-dimensional motion measurement devices or the like, or a coordinate input apparatus serving as an application software, is realized by the following methods:
(1) A method utilizing a sensor supported by a multiarticulated mechanism to detect the three dimensional position of a coordinate-inputting object by a mechanical contact between the sensor and the object or mechanical deformation;
(2) A method which realizes three-dimensional coordinate input by combination of second-dimensional input operations using a joy stick or the like; and
(3) A method which calculates the three-dimensional coordinates by executing computation processing of a stereo-image obtained by a plurality of video cameras or the like, which are capable of sensing visible light or infrared ray.
However, the method (1) of the foregoing conventional coordinate input apparatus is difficult to apply to various usage because of its large mechanism. The method (2) has a disadvantage in that a user is unable to intuitively perform three-dimensional coordinate input and that the three-dimensional coordinate input cannot be realized in real time or continuously. The method (3) has a problem of an excessive amount of operations which impose a heavy load on a CPU of a computer, does not execute real-time processing; and causes a delay in other processing.
Also, proposed as a coordinate input apparatus for inputting two-dimensional coordinates with the use of the coordinate input mechanism of the aforementioned coordinate input apparatus is to input coordinate data designated by an operator with a pointing device to an external apparatus such as a computer or the like.
As such coordinate input apparatus, for instance, a light spot formed on a display screen of a large display by an operator with a pointing device is picked up by a CCD area sensor or a linear sensor, and based on an output signal indicative of the position of the light spot focused in the image sensing surface of the sensor, two-dimensional coordinates of height spot on the display screen are obtained. Alternatively, a plurality of position detection devices which output analog signals corresponding to the position of the light spot are used, and based on the level or rate of analog voltages outputted by the position detection devices, two-dimensional coordinates of the light spot on the display screen are obtained.
Such coordinate input apparatus utilizing a light beam must achieve the following.
(1) To generate a highly precise coordinate value and to enable stable input operation, an influence of disturbance light incident from outside the coordinate input apparatus must be eliminated.
Recently, as the displaying methods are diversified, and the use of infrared ray as a wireless communication means is generalized and a remote controller employing an infrared ray is widely used, many infrared rays are utilized in the environment in which a coordinate input apparatus is used. In order to accurately perform operation of the coordinate input apparatus in such environment, means which assures disturbance light removal is required.
(2) The coordinate input apparatus must have a wide photoreceptive dynamic range.
Generally in the type of coordinate input apparatus which detects a light beam emitted from a pointing device operated by a user, the amount of light emitted from the pointing device fluctuates largely in accordance with how the user operates the pointing device (more specifically, the direction or moving speed of the pointing device or the distance between the pointing device and a sensor). Furthermore, when battery power is used to drive the pointing device, the amount of light emitted from the pointing device largely varies depending on the remaining amount of power in the battery. Therefore, the coordinate input apparatus of this type needs photoreceptive means having a wide dynamic range.
However the foregoing coordinate input apparatus, which detects a light spot on the display screen, only includes an optical filter for filtering light of a particular wavelength band as the means for removing disturbance light. No consideration is given to make the optical detection of the coordinate input apparatus follow the fluctuating amount of light emitted.
Furthermore, also in the case of the aforementioned type of coordinate input apparatus which detects the level or rate of analog voltages outputted by the plurality of position detection devices, the only means provided for removing disturbance light is a filter for filtering light of a particular wavelength band. Since the coordinate input apparatus of this type detects coordinates by using a level of photoreception signal indicative of the amount of light emitted, it is almost impossible to make the optical detection of the coordinate input apparatus follow the fluctuating amount of light emitted.